This invention relates to an adjustable seal lubrication hydraulic positioning device. More specifically, this invention relates to a runner seal positioning system particularly useful for a hydroelectric power generator turbine.
Hydroelectric power generation inherently involves exposing large, expensive machinery to water under high pressures. The possibility of water contamination poses a contstant threat to oil-lubricated parts of the machinery. One such part is the oil gallery of the turbine scroll case, which supports the upstream end of the turbine.
In a conventional hydroelectric turbine, such as the turbines at the Jarvis Hydroelectric Power Project in Hinckley, N.Y., the oil gallery is protected by a runner seal assembly and a labyrinth seal. Water first encounters the runner seal assembly and leaks into a runner seal cavity, where it drains through a runner seal cavity drain line. The runner seal assembly reduces the pressure of the water before the water encounters a labyrinth seal, which itself protects the oil gallery.
To lubricate and to provide cooling for the runner seal, it is necessary to allow some water leakage through the runner seal assembly. However, if too much water is allowed to leak into the runner seal cavity, the capacity of the runner seal cavity drain line will be exceeded and water pressure will build in the runner seal cavity, ultimately forcing water through the labyrinth seal and into the oil gallery and contaminating the lubrication oil.
Weighing these two considerations, it has been found at the turbines of the Jarvis Hydroelectric Power Project that an optimum rate of leakage past the runner seal assembly is from 5 to 10 gallons per minute. The leakage rate is influenced by such factors as the water level of the supply reservoir and the generation output of the turbines, both of which can vary. In particular, reservoir water levels are subject to rapid changes during the spring thaw.
Accordingly, the runner seal assembly must be able to accomodate changing conditions to keep the leakage rate in the optimum range. This is conventionally accomplished by utilizing a manually adjustable source of pressurized water to provide a back pressure to the runner seal. An increase in the back pressure tightens the runner seal assembly and reduces the leakage rate, while a decrease in the back pressure loosens the seal and allows a greater leakage rate. This adjustment process is called positioning the runner seal. The leakage rate is monitored continually, and maintenance personnel are called in to adjust the back pressure as needed.
This system of adjusting the leakage rate has proven to be wasteful in both time and expense. The need for adjusting piston back pressure causes frequent, irregular, and unwelcome interruptions in the schedules of maintenance workers. Moreover, in the time that passes between the onset of a non-optimal leakage rate and the correction of the leakage rate, the turbine undergoes excessive wear. Periods of a low leakage rate cause premature wear of the runner seal assembly, and periods of high leakage rate introduce water to the oil gallery.